What is progesterone, and what does it do?

Verily’s resident expert Dr. A. Nicky Hjort, M.D., OB-GYN, says progesterone is a class of hormone your body makes (or should make) in the ovaries during each menstrual cycle. In a normal menstrual cycle, progesterone levels rise after ovulation in order to sustain the lining of the uterus which thickens each month for a potential pregnancy, Dr. Hjort says. “When [the] uterus realizes that pregnancy has not occurred,” progesterone levels fall and the uterus “cleans house and washes out the lining, and that’s your menstrual cycle.” When pregnancy does occur, progesterone production maintains the uterine lining and should remain high throughout the pregnancy.

Because of its critical role in a normal menstrual cycle and a healthy pregnancy, irregular periods, infertility, and miscarriage could all be related to low progesterone levels. Symptoms of low progesterone for women who aren’t pregnant include:

headaches or migraines

mood changes, including anxiety or depression

low libido

hot flashes

irregular menstrual cycle

weight gain

fibroids, endometriosis

thyroid dysfunction

In women who are pregnant, symptoms include:

constant breast tenderness

unrelenting fatigue

frequent low blood sugar

vaginal dryness

Simple blood tests can determine your progesterone levels.

A Better Alternative to Treating Irregular Periods

Women with irregular periods are often prescribed combination birth control pills, which commonly contain one of many types of synthetic progesterone, namely, progestin (the other major component being estrogen). For women with irregular bleeding who aren’t interested in oral contraceptive pills or a hysterectomy, taking progestin “alone and by itself” is a standard course of treatment, Dr. Hjort says. She cautions that most of the hormonal effects that increase the risk of breast cancer in women who take birth control are believed to result from the progestin, not the synthetic estrogen, so the risk remains with this hormonal treatment.

When taken alone, progestin doesn’t prevent pregnancy; it only stabilizes the lining of the uterus. Dr. Hjort says it’s prescribed to regulate cycles in women who are trying to conceive or who can’t take estrogen because of a history of certain liver problems, cancers, or blood clots.

Most commonly, a patient will be given a ten-day course of progesterone. When she stops taking the supplement, the lack of progesterone triggers a “reboot” in her system and her normal period will begin. In certain situations—women with a history of depression, diabetes, or abnormal cholesterol—a lower dose or a shorter time frame may be prescribed. Dr. Hjort calls this treatment “a kind of trickery to keep the uterus calm and the cycle short and regular.” It’s possible to see “a 20 to 30 percent reduction in length of flow, heaviness of flow, and massive improvement of regularity in women who have irregular cycles,” she says.

The Infertility & Miscarriage Debate

Dr. Hjort cites progesterone in pregnancy as an area of “intense debate” among OB-GYNs and reproductive endocrinologists (sub-specialists who manage infertility, recurrent pregnancy loss, and hormonal imbalances in women). “Half of them believe that a progesterone deficiency is a real thing and the other half of them believe that it’s just a big, fat hoax,” says Dr. Hjort.

Low progesterone is often attributed to recurrent pregnancy loss, in part because testing on women who have experienced multiple miscarriages often shows an insufficient amount of progesterone. But Dr. Hjort says it’s a case of the chicken or the egg: “Did the low progesterone level cause the miscarriage or did the miscarriage cause the low progesterone level?” No one really knows. But this observation has led to developing a diagnosis called a luteal phase defect: “an inadequate amount of natural progesterone in the uterus to maintain the lining and sustain the pregnancy.”

Taking a daily progesterone supplement is purported to help maintain the uterine lining, but it’s typically only offered after two or three miscarriages. While progesterone isn’t dangerous, doctors often don’t want to give medication unless it’s necessary. Since miscarriage is so common, and can be a result of a whole host of things from improper implantation to a chromosomal abnormality in the baby, OBGYNs don’t immediately presume there is an underlying condition in the mother that caused it.

Dr. Hjort notes that when progesterone seems to work, it’s possible that the patient was going to sustain the pregnancy anyway. Because there is solid research on both sides of the debate, she believes there is something science hasn’t figured out yet, and progesterone just happens to help with whatever underlying condition(s) there may be. It could well be that the progesterone truly solves the problem; but the science isn’t yet certain of what that “problem” is.

The Bottom Line

If you have had one or more of these issues, ask your doctor about looking into a progesterone test. Progesterone therapy could be the answer to an issue that was misdiagnosed or left unexplained, but that also doesn’t mean it’s a cure-all. Luckily, the risks of supplementing with progesterone are “probably low, if anything at all,” says Dr. Hjort, at least in the short term. Common side effects include mild headache, mild nausea, dizziness, and breast tenderness. Time and research will tell if there are long-term side effects.

Whether we know it or not, we will all cross paths with women who experience irregular cycles, infertility, and miscarriage. We should keep progesterone on our radars and educate others about it. The future of women’s health depends on us.

Obinna Onyia

I had irregular periods for years &’ was always depressed about it because i heard having irregular periods would mean itd be harder to get pregnant. it took me 3 years to finally be able to conceive on my own. But now i have 2 beautiful boys and im more then happy !!!